This invention relates to a rotary fluid pump in which fluid intake, compression and discharge operations are carried out by the movement of vanes accompanied by the rotation of a rotor. More particularly, this invention relates to a type thereof wherein a pair of resilient sealing plates are sealingly disposed each between a main body of a stator housing and end head to define end chambers each between the sealing plate and a recessed portion of the end head.
Within the prior art rotary fluid pumps have been provided with a rotor chamber defined between the main body of the housing and end heads disposed at both sides of the housing. A rotor is rotationally supported in the housing by a drive shaft supported by bearings in a cantilevered manner or in an inboard manner. a plurality of vane grooves are formed in the rotor to slidingly receive an equal number of the vanes adapted to move along the radial direction of the rotor contacting with the inner peripheral surface of the main body or of a sleeve force-fitted with the main body. These vanes are rotated together with the rotation of the rotor to thereby perform fluid intake, compression and discharge operations.
According to such a prior art pump, sealability between side faces of the rotor and the end heads is particularly important, and therefore, resilient sealing plates are sealingly disposed between the main body of the housing and the end head. Further, a pair of end chambers are provided each between the sealing plate and the end head to allow resilient deformation of the sealing plates, to thereby ensure a seal between the side faces of the rotor and the seal plates.
The rotary fluid pump having sealing plates generally forms fluid inlet and outlet ports in the main body of the housing. With this structure, since radially outer end portions of the vanes permit sliding contact with the inner peripheral surface of the housing, stepped portions are created on the end portion of the vanes at the position corresponding to the inlet and outlet ports. The stepped portion due to wear differential may degrade sealability between the vanes and the inner peripheral surface of the main body.
In order to obviate this drawback, fluid inlet and outlet ports are formed in the seal plate(s) and fluid intake and discharge holes are formed in the end head(s) to introduce and discharge fluid into and from the rotor chamber through the end chamber(s). However, grease in the bearing disposed in a bearing support portion of the end head may be sucked by intake pressure or the grease may be expelled therefrom by the discharging pressure.